(a) Demonstration of a neurotrophic factor in crude extracts of the CNS for the maintenance of the acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) contents of the preganglionically denervated superior cervical ganglion (SCG) of the cat will be followed up by: (a) investigation of its mechanism of action and (b) initiation of a program to isolate and characterize the action factor. The mechanisms by which aprotinin and continual anesthesia with sodium pentobarbital oppose the fall in AChE and BuChE in denervated SCG will also be studied. The investigation of the site of origin of BuChE in the ganglion cells of the cat SCG will be continued. The electron microscopic (EM) localizations of AChE and BuChE in the carotid body, retina, olfactory tubercle, adrenal medulla, and other selected tissues will be studied. (2) New approaches will be used in attempting to localize the sodium dependent high affinity choline uptake (SDHACU) system histochemically. (3) A histochemical method will be sought for the localization of neurotoxic esterase (NTE), the enzyme whose inactivation has been proposed as the mechanism for the production of delayed neurotoxicity (DN) by certain organophosphates. (4) Histochemical investigation of the distinction between monoamine oxidase (MAO) A and B will be continued.